1. Field of the Invention
The present invention relates to a driving device, and more particularly, the present invention relates to a driving device for a passive module.
2. Description of the Related Art
A driving device is needed to drive a passive module. For example, the liquid crystal display (LCD) panel needs a driving device with high precision. The LCD panel has a pixel array. Taking the LCD panel with resolution of 1024×768 as an example. The LCD panel has 768 rows and each row has 1024×3 pixels with red, blue, and green colors. The pixels are controlled by a number of data lines and scan lines, and pixels are scanned sequentially by enabling the corresponding scan line. Pixel data transmitted by the data line determine the luminous of the corresponding pixels in the scanned row. A frame of image is displayed after 768 rows of pixels are scanned.
FIG. 1 is a block diagram of the conventional parallel driving device of the passive module. The passive module 160 can be a LCD panel, such as the thin film transistor (TFT) LCD panel or the liquid crystal on silicon (LCOS) panel. When displaying one row of pixels, 1024×3 digital pixel data D are input into a data buffer 120 of the passive module 160. The shift register 110 sequentially turns on each of the buffering units (not shown in FIG. 1) of the data buffer 120, so as to allow each pixel data to be latched in sequence into the corresponding buffering unit. The data buffer 120 includes at least 1024×3 buffer units. The shift register 110 can turn on or off the buffer units, so as to determine which buffer units are enabled to store the pixel data. If four buffer units, such as the first buffer unit to the fourth buffer unit, are turned on simultaneously, the corresponding pixel data D are input to the turned-on buffer units. Afterward, the shift register 110 will turn on the next four buffer units, such as the 5th buffer unit to the 8th buffer unit, to store the corresponding pixel data. All pixel data corresponding to one row of pixels are stored in the data buffer 120 after the turning on and off procedure of the shift register 110 is performed for 256×3 times (1024×3/4=256×3).
Then the pixel data is fed from the data buffer 120 to the voltage level converter 130 in parallel, so as to adjust the voltage level of the pixel data D. Then, a digital-to-analog converter 140 converts the adjusted pixel data D into an analog pixel data in parallel. Finally, the 1024×3 analog pixel data are input to the passive module 160 via the output buffer unit 150 in parallel.
In the conventional parallel driving device, since there are 1024×3 pixels for each row, the data buffer 120, the voltage level converter 130, and the digital-to-analog converter 140 each should be implemented with 1024×3 process units, so as to respectively process the pixel data for each of the pixels in parallel. Due to the increased integration, the hardware size is increased, the yield of production is reduced and the fabrication cost is increased.
Besides, the output buffer unit 150 can be implemented by a number of operational amplifiers, which function as an output buffer. The analog pixel data which the output buffer unit 150 received is amplified by the operational amplifiers. The amplified analog data is then applied to data lines of the passive module 160. However, the offset of the operational amplifiers are not equal to each other. Thus, even when the analog data with the same voltage corresponding to the same gray level is input to the operational amplifiers, the output voltages of these operational amplifiers are different. Therefore, it is necessary to provide a way to solve the problem caused from the different offset of the operational amplifiers.